Technique for determining performance characteristics of electronic devices and systems

ABSTRACT

A technique for determining performance characteristics of electronic devices and systems is disclosed. In one embodiment, the technique is realized by measuring a first response on a first transmission line from a single pulse transmitted on the first transmission line, and then measuring a second response on the first transmission line from a single pulse transmitted on at least one second transmission line, wherein the at least one second transmission line is substantially adjacent to the first transmission line. The worst case bit sequences for transmission on the first transmission line and the at least one second transmission line are then determined based upon the first response and the second response for determining performance characteristics associated with the first transmission line.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation of U.S. patent applicationSer. No. 13/245,234, filed Sep. 26, 2011, which is a continuation ofU.S. patent application Ser. No. 12/471,044, filed May 22, 2009, nowU.S. Pat. No. 8,055,458, which is a continuation of U.S. patentapplication Ser. No. 11/354,964, filed Feb. 16, 2006, now U.S. Pat. No.7,542,857, which is a divisional of U.S. patent application Ser. No.10/954,489, filed Oct. 1, 2004, now U.S. Pat. No. 7,006,932, which is acontinuation of U.S. patent application Ser. No. 09/799,516, filed Mar.7, 2001, now U.S. Pat. No. 6,920,402, each of which is herebyincorporated by reference herein in its entirety.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to integrated circuit testingsystems and, more particularly, to a technique for determiningperformance characteristics of electronic devices and systems.

BACKGROUND OF THE DISCLOSURE

A typical data transmission system comprises a transmitter, a receiver,and some form of transmission medium for carrying a data signal from thetransmitter to the receiver. A common problem that occurs in such a datatransmission system is that the data signal arriving at the receiver maybe distorted by Inter-Symbol Interference (ISI). That is, the timing andvoltage margins at the receiver are typically dependent upon thetransmitted data.

ISI generally occurs due to two mechanisms. First, the timing or voltageof a data signal presently being transmitted on any given transmissionline may be affected by residual reflections from prior transmitted datasignals on the same transmission line. Second, adjacent transmissionlines may have electromagnetic coupling. In such a case, the timing orvoltage of data signals transmitted on a given transmission line may beinfluenced by data signals transmitted on other adjacent transmissionlines.

When testing data transmission devices or systems, the operation of suchdevices or systems is often measured by transmitting long sequences ofrandom data. To some degree, the accuracy of this approach depends uponthe probability of the random sequence containing a worst case datapattern. The accuracy of this approach is also dependent upon whetherthere is significant ISI associated with the device or system. Further,the measurement apparatus may exhibit ISI, thereby introducing anadditional uncertainty. In some cases, guard-banding is employed to dealwith these uncertainties.

Referring to FIG. 1, there is shown a typical apparatus 10 for testingthe operation of an integrated circuit (IC) memory device 12. Theapparatus 10 comprises a vector memory 14 for storing random datasequences. The vector memory 14 is connected to a transmitter 16 fortransmitting the random data sequences along a transmission line 18 tothe IC memory device 12. The apparatus 10 also comprises a receiver 20for receiving data transmitted from the IC memory device 12 via thetransmission line 18, and a result memory 22, connected to the receiver20, for storing the received data. The operation of the IC memory device12 is tested by comparing the random data sequences that are transmittedfrom the vector memory 14 to the IC memory device 12 for storage thereinwith the same random data sequences after they are transmitted from theIC memory device 12 to the result memory 22 for storage therein. Itshould be noted that although only one transmitter 16, transmission line18, and receiver 20 are shown, this arrangement may be duplicated asrequired based upon the number of input/output (I/O) lines of the ICmemory device 12 to be measured.

The apparatus 10 can also be used to attempt to measure the worst casetiming and voltage margins of the IC memory device 12 by measuring theoutput waveforms of the random data sequences after they are transmittedfrom the IC memory device 12 to the result memory 22. However, sincethere is no way to know when a worst case random data sequence willoccur, every output waveform must be measured. Also, this method is notguaranteed to find the worst case timing and voltage margins since therandom data sequences may not include the worst case random datasequence. This is especially true when the outputs of the IC memorydevice 12 are affected by ISI. In addition, if the apparatus 10 itselfhas ISI, the measurement result will not accurately reflect the trueworst case timing and voltage margins of the IC memory device 12.

In view of the foregoing, it would be desirable to provide a techniquefor determining performance characteristics of electronic devices andsystems which overcomes the above-described inadequacies andshortcomings.

SUMMARY OF THE DISCLOSURE

A technique for determining performance characteristics of electronicdevices and systems is disclosed. In one embodiment, the technique isrealized by measuring a first response on a first transmission line froma single pulse transmitted on the first transmission line, and thenmeasuring a second response on the first transmission line from a singlepulse transmitted on at least one second transmission line, wherein theat least one second transmission line is substantially adjacent to thefirst transmission line. The worst case bit sequences for transmissionon the first transmission line and the at least one second transmissionline are then determined based upon the first response and the secondresponse for determining performance characteristics associated with thefirst transmission line.

In accordance with other aspects of the present disclosure, determiningworst case bit sequences beneficially includes determining worst casetiming margin bit sequences and worst case voltage margin bit sequencesfor transmission on the first transmission line and the at least onesecond transmission line.

In a first case, determining worst case timing margin bit sequences fortransmission on the first transmission line beneficially comprisesdetermining the polarity of the first response at data-cell boundariesof the first response. If the polarity at a data-cell boundary ispositive, then an associated bit in a first worst case timing margin bitsequence for transmission on the first transmission line is beneficiallyassigned a logic one value. Alternatively, if the polarity at adata-cell boundary is negative, then an associated bit in the firstworst case timing margin bit sequence for transmission on the firsttransmission line is beneficially assigned a logic zero value.Furthermore, if the polarity at a data-cell boundary is positive, thenan associated bit in a complementary worst case timing margin bitsequence for transmission on the first transmission line is beneficiallyassigned a logic zero value. Alternatively, if the polarity at adata-cell boundary is negative, then an associated bit in acomplementary worst case timing margin bit sequence for transmission onthe first transmission line is beneficially assigned a logic one value.

In a second case, determining worst case timing margin bit sequences fortransmission on the at least one second transmission line beneficiallycomprises determining the polarity of the second response at data-cellboundaries of the second response. If the polarity at a data-cellboundary is positive, then an associated bit in a first worst casetiming margin bit sequence for transmission on the at least one secondtransmission line is beneficially assigned a logic one value.Alternatively, if the polarity at a data-cell boundary is negative, thenan associated bit in the first worst case timing margin bit sequence fortransmission on the at least one second transmission line isbeneficially assigned a logic zero value. Furthermore, if the polarityat a data-cell boundary is positive, then an associated bit in acomplementary worst case timing margin bit sequence for transmission onthe at least one second transmission line is beneficially assigned alogic zero value. Alternatively, if the polarity at a data-cell boundaryis negative, then an associated bit in a complementary worst case timingmargin bit sequence for transmission on the at least one secondtransmission line is beneficially assigned a logic one value.

In a third case, determining worst case voltage margin bit sequences fortransmission on the first transmission line beneficially comprisesdetermining the polarity of the first response at the center ofdata-cells of the first response. If the polarity at the center of adata-cell is positive, then an associated bit in a first worst casevoltage margin bit sequence for transmission on the first transmissionline is beneficially assigned a logic one value. Alternatively, if thepolarity at the center of a data-cell is negative, then an associatedbit in the first worst case voltage margin bit sequence for transmissionon the first transmission line is beneficially assigned a logic zerovalue. Furthermore, if the polarity at the center of a data-cell ispositive, then an associated bit in a complementary worst case voltagemargin bit sequence for transmission on the first transmission linebeneficially is assigned a logic zero value. Alternatively, if thepolarity at the center of a data-cell is negative, then an associatedbit in a complementary worst case voltage margin bit sequence fortransmission on the first transmission line is beneficially assigned alogic one value.

In a fourth case, determining worst case voltage margin bit sequencesfor transmission on the at least one second transmission linebeneficially comprises determining the polarity of the second responseat the center of data-cells of the second response. If the polarity atthe center of a data-cell is positive, then an associated bit in a firstworst case voltage margin bit sequence for transmission on the at leastone second transmission line is beneficially assigned a logic one value.Alternatively, if the polarity at the center of a data-cell is negative,then an associated bit in the first worst case voltage margin bitsequence for transmission on the at least one second transmission lineis beneficially assigned a logic zero value. Furthermore, if thepolarity at the center of a data-cell is positive, then an associatedbit in a complementary worst case voltage margin bit sequence fortransmission on the at least one second transmission line isbeneficially assigned a logic zero value. Alternatively, if the polarityat the center of a data-cell is negative, then an associated bit in acomplementary worst case voltage margin bit sequence for transmission onthe at least one second transmission line is beneficially assigned alogic one value.

In an alternative embodiment, an improved integrated circuit device isdisclosed having a plurality of data transmitters for transmitting datafrom the integrated circuit device onto respective ones of a pluralityof transmission lines. The improvement comprises a plurality of pulsegenerators electrically connected to respective ones of the plurality ofdata transmitters. Each of the plurality of pulse generators generates asingle pulse data signal for transmission by a respective datatransmitter onto a respective transmission line so as to provide asingle bit response associated with at least one of the plurality oftransmission lines when a first response is measured on a first of theplurality of transmission lines when a respective first data transmittertransmits a single pulse data signal generated by a respective firstpulse generator on the first transmission line, and when a secondresponse is measured on the first transmission line when at least onesecond of the plurality of data transmitters transmits a single pulsedata signal generated by at least one respective second pulse generatoron at least one respective second transmission line. The at least onerespective second transmission line is typically substantially adjacentto the first transmission line.

In another alternative embodiment, an improved integrated circuit deviceis disclosed having at least one data receiver for receiving datasignals from at least one respective transmission line. The improvementcomprises a comparator circuit electrically connected to the at leastone respective transmission line for acquiring timing and voltagecharacteristics of data signals propagating along the at least onetransmission line prior to being received by the at least one datareceiver.

In accordance with other aspects of the present disclosure, thecomparator circuit beneficially comprises a comparator device forcomparing the voltage level of the data signals propagating along the atleast one transmission line with a reference voltage level. Thecomparator circuit also further beneficially comprises a clockmultiplier for multiplying a clock signal to provide the comparatordevice with an appropriate sample rate.

In still another alternative embodiment, an improved integrated circuitdevice is disclosed having at least one data receiver for receiving datasignals from at least one respective transmission line. The improvementcomprises a converter circuit electrically connected to the at least onerespective transmission line for acquiring timing and voltagecharacteristics of data signals propagating along the at least onetransmission line prior to being received by the at least one datareceiver.

In accordance with other aspects of the present disclosure, theconverter circuit beneficially comprises an analog-to-digital converterdevice for converting the analog voltage level of the data signalspropagating along the at least one transmission line into a digitalvoltage level. The converter circuit also further beneficially comprisesa clock multiplier for multiplying a clock signal to provide theanalog-to-converter device with an appropriate sample rate.

The present disclosure will now be described in more detail withreference to exemplary embodiments thereof as shown in the appendeddrawings. While the present disclosure is described below with referenceto exemplary embodiments, it should be understood that the presentdisclosure is not limited thereto. Those of ordinary skill in the arthaving access to the teachings herein will recognize additionalimplementations, modifications, and embodiments, as well as other fieldsof use, which are within the scope of the present disclosure asdescribed herein, and with respect to which the present disclosure maybe of significant utility.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to facilitate a fuller understanding of the present disclosure,reference is now made to the appended drawings. These drawings shouldnot be construed as limiting the present disclosure, but are intended tobe exemplary only.

FIG. 1 shows a typical prior art apparatus for testing the operation ofan integrated circuit (IC) memory device.

FIG. 2 shows an apparatus for determining the worst case performancecharacteristics of an integrated circuit (IC) device in accordance withthe present disclosure.

FIG. 3 shows an example worst case bit sequence that is divided intopreamble and rising edge bits.

FIG. 4 shows a model transmission line representative of thetransmission line shown in FIG. 2 and adjacent transmission lines.

FIG. 5 illustrates a first waveform that is acquired when a single databit is transmitted on a victim transmission line while adjacentaggressor transmission lines are inactive, and a second waveform that isacquired when a single data bit is transmitted on adjacent aggressortransmission lines while the victim transmission line is inactive; thesetwo waveforms representing the single bit response (SBR) of the ICdevice shown in FIG. 2.

FIG. 6 illustrates how the first waveform of FIG. 5 is examined todetermine the polarity of the SBR of the IC device shown in FIG. 2 andthus the worst case timing margin bit sequence for the victimtransmission line.

FIG. 7 illustrates how the second waveform of FIG. 5 is examined todetermine the polarity of the SBR of the IC device shown in FIG. 2 andthus the worst case timing margin bit sequence for the aggressortransmission lines.

FIG. 8 illustrates how reflection noise is added on the victimtransmission line of FIG. 2 when the worst case timing margin bitsequence for the victim transmission line is transmitted on the victimtransmission line.

FIG. 9 illustrates how the first waveform is examined to determine thepolarity of the SBR of the IC device of FIG. 2 and thus the worst casevoltage margin bit sequence for the victim transmission line.

FIG. 10 illustrates how the second waveform is examined to determine thepolarity of the SBR of the IC device of FIG. 2 and thus the worst casevoltage margin bit sequence for the aggressor transmission lines.

FIG. 11 shows an alternative embodiment of the present disclosurewherein a comparator circuit is beneficially contained in a receiver ofa data transmission system such that the worst case performancecharacteristics of the entire data transmission system can bedetermined.

FIG. 12 shown an alternative embodiment of the present disclosurewherein an analog-to-digital converter circuit is beneficially containedin a receiver of a data transmission system such that the worst caseperformance characteristics of the entire data transmission system canbe determined.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Referring to FIG. 2, there is shown an apparatus 30 for determining theworst case performance characteristics of an integrated circuit (IC)device 32 in accordance with the present disclosure. The apparatus 30comprises a transmission line 34 for receiving data signals from the ICdevice 32, and an oscilloscope 36 for capturing the timing and voltagecharacteristics of the received data signals. The apparatus 30 alsocomprises a computer 38 for calculating the worst case performancecharacteristics of the IC device 32 based upon the captured timing andvoltage characteristics of the received data signals in accordance withthe methods described below.

The IC device 32 comprises a memory array 40 for storing data. The ICdevice 32 also comprises a receiver 42 for receiving data from thetransmission line 34 for storage in the memory array 40, and atransmitter 44 for transmitting data from the memory array 40 and ontothe transmission line 34 for transmission to the apparatus 30. The ICdevice 32 further comprises a single pulse generator 46 for generating asingle pulse data signal to be transmitted by the transmitter 44 ontothe transmission line 34 for transmission to the apparatus 30.

At this point it should be noted that although only one receiver 42,transmitter 44, single pulse generator 46, transmission line 34, andoscilloscope 36 are shown, this arrangement may be duplicated asrequired based upon the number of input/output (I/O) lines of the ICdevice 32 to be measured.

It should also be noted that although the IC device 32 is shown in thisparticular embodiment as a memory device, the present disclosure is notlimited in this regard. For example, it is within the scope of thepresent disclosure to utilize the methods described herein to determinethe worst case performance characteristics of other types of electronicdevices and systems, such as microprocessors, application specificintegrated circuits (ASICs), and digital data busses.

In overview, the apparatus 30 is configured such that the worst case bitsequences and output margins of the IC device 32 can be calculated bymeasuring the single bit response (SBR) of the IC device 32. This SBRmeasurement involves acquiring two different waveforms at theoscilloscope 36. The first waveform is acquired when a single pulse datasignal is generated by the single pulse generator 46 and transmitted bythe transmitter 44 onto the transmission line 34. The second waveform isacquired when a single pulse data signal is generated and transmittedonto one or more adjacent transmission lines (not shown). Worst case bitsequences are then determined based upon these two acquired waveforms,as described in detail below. The worst case output margins of the ICdevice 32 can then be determined by having the IC device 32 transmit theworst case bit sequences and then measuring the resultant outputwaveforms at the oscilloscope 36. It should be noted, however, thatthere is no need to have the IC device 32 actually transmit the worstcase bit sequences to determine the worst case output margins of the ICdevice 32. That is, as long as the system is linear and time invariant,the worst case output margins can be calculated by linear addition ofsimple responses, such as the SBR. Even if the system is nonlinear ortime variant, as long as the non-linearity is weak, nearly worse caseoutput margins can still be derived.

The worst case bit sequences are designed to produce worst case outputmargins (both timing and voltage) for specific edges (both rising orfalling). The edges are typically distorted by reflections from datapreviously transmitted on the transmission line 34, as well as by datatransmitted on adjacent transmission lines (not shown). Referring toFIG. 3, each worst case bit sequence is typically divided into twoparts. The first part, called the “preamble”, sets-up the reflections inadvance. The second part comprises two bits which create either a risingedge (i.e., bits 01) or a falling edge (i.e., bits 10). The examplepresented in FIG. 3 shows a hypothetical preamble which causes worstcase timing distortion. For example, assume that Preamble-A shifts therising edge early. Then, its inverse, Preamble-B, will shift the risingedge late. This is true as long as the system is linear and timeinvariant.

The transmission line 34 can be one of multiple transmission lines of adata bus. If such is the case, the previously described adjacenttransmission lines (not shown) typically make up the other transmissionlines of the data bus. For purposes of example in this detaileddescription, it is assumed that this is the case. More particularly, itis assumed that transmission line 34 is the fourth bit (i.e., bit 3) ofan eight bit data bus and the previously described adjacent transmissionlines (not shown) make up the other bits (i.e., bits 0, 1, 2, 4, 5, 6,and 7) of the eight bit data bus. Referring to FIG. 4, there is shown amodel transmission line representative of transmission line 34 and eachof the previously described adjacent transmission lines (not otherwiseshown). This model transmission line comprises a transmitter (i.e., acurrent mode driver) 50, a receiver 52, and a non-ideal transmissionline 54 that is terminated by a resistor 56 located at a first end ofthe non-ideal transmission line 54. Alternatively, the non-idealtransmission line 54 may also be terminated by a second resistor locatedat a second end of the non-ideal transmission line 54. The transmissionline 54 is non-ideal in that it has non-uniform impedance and issusceptible to coupling from adjacent transmission lines (not shown). Itshould be noted that worst case coupling occurs when the data that istransmitted on the adjacent transmission lines (not shown) is differentfrom the data that is transmitted on transmission line 54. For thisreason, and with respect to FIG. 2, transmission line 34 is referred toas the “victim” transmission line while the adjacent transmission lines(not shown) are referred to as the “aggressor” transmission lines.

Referring back to FIG. 2, the worst case bit sequences are determined byfirst measuring the SBR of the IC device 32. As previously mentioned,the SBR measurement involves acquiring two different waveforms at theoscilloscope 36. The first waveform is acquired when a single data bitis transmitted on the victim transmission line 34 while the adjacentaggressor transmission lines (not shown) are inactive. The secondwaveform is acquired when a single data bit is transmitted on theadjacent aggressor transmission lines (not shown) while the victimtransmission line 34 is inactive. FIG. 5 illustrates the first waveform60 and the second waveform 62. These two waveforms 60 and 62 representthe SBR of the IC device 32.

From the first waveform 60 and the second waveform 62 it can bedetermined how long it takes for significant reflections to decay on thevictim transmission line 34. This reflection decay time period is usedto set the length of the preamble of the worst case bit sequences. Forexample, the first waveform 60 and the second waveform 62 show that thevictim transmission line 34 returns to a quiescent level after 4 bittimes. Therefore, the length of the preamble of the worst case bitsequences for the worst case timing margin is 4 bits long.

Once the SBR of the IC device 32, and hence the length of the preambleof the worst case bit sequences, is obtained, the worst case bitsequences for both the victim transmission line 34 and the adjacentaggressor transmission lines (not shown) for determining the worst casetiming margin of the IC device 32 can be obtained. These worst casetiming margin bit sequences are obtained by first determining the worstcase timing margin bit sequence for the victim transmission line 34.This is accomplished by examining the first waveform 60.

Referring to FIG. 6, the first waveform 60 is examined to determine thepolarity of the SBR of the IC device 32. That is, the worst case timingmargin bit sequence for the victim transmission line 34 that will shiftthe victim transmission line timing in one direction (i.e., shift therising edge early) is a logic 01 bit pattern (i.e., to yield a risingedge) preceded by four bits whose values depend on the polarity of theSBR of the IC device 32 at each data-cell boundary. Thus, the firstwaveform 60 is examined to determine the polarity of the SBR of the ICdevice 32 at each data-cell boundary. If the polarity at a data-cellboundary is positive, then the associated bit in the worst case timingmargin bit sequence for the victim transmission line 34 is a logic one.Conversely, if the polarity at a data-cell boundary is negative, thenthe associated bit in the worst case timing margin bit sequence for thevictim transmission line 34 is a logic zero.

The order of the bits in the worst case timing margin bit sequence forthe victim transmission line 34 is determined by the order of thedata-cell boundaries. That is, the bit value determined from thepolarity of the most recent data-cell boundary is the first bit in theworst case timing margin bit sequence for the victim transmission line34, the bit value determined from the polarity of the next most recentdata-cell boundary is the second bit in the worst case timing margin bitsequence for the victim transmission line 34, and so on until the lastdata-cell boundary is reached. So, for the example shown in FIG. 6, theworst case timing margin bit sequence for the victim transmission line34 is 101001. As previously mentioned, this worst case timing margin bitsequence for the victim transmission line 34 will shift the victimtransmission line timing in one direction (i.e., shift the rising edgeearly). To shift the victim transmission line timing in the oppositedirection (i.e., shift the rising edge late), the last two bits remainthe same, and the precursor bits are inverted. Thus, for the exampleshown in FIG. 6, the complementary worst case timing margin bit sequencefor the victim transmission line 34 is 010101.

To obtain the worst case timing margin bit sequence for the aggressortransmission lines, the second waveform 62 is examined. Referring toFIG. 7, the second waveform 62 is examined to determine the polarity ofthe SBR of the IC device 32. That is, the worst case timing margin bitsequence for the aggressor transmission lines is six data bits long. Thevalues of the six data bits depend on the polarity of the SBR of the ICdevice 32 at each data-cell boundary. Thus, the second waveform 62 isexamined to determine the polarity of the SBR of the IC device 32 ateach data-cell boundary. If the polarity at a data-cell boundary ispositive, then the associated bit in the worst case timing margin bitsequence for the aggressor transmission lines is a logic one.Conversely, if the polarity at a data-cell boundary is negative, thenthe associated bit in the worst case timing margin bit sequence for theaggressor transmission lines is a logic zero.

The order of the bits in the worst case timing margin bit sequence forthe aggressor transmission lines is determined by the order of thedata-cell boundaries. That is, the bit value determined from thepolarity of the most recent data-cell boundary is the first bit in theworst case timing margin bit sequence for the aggressor transmissionlines, the bit value determined from the polarity of the next mostrecent data-cell boundary is the second bit in the worst case timingmargin bit sequence for the aggressor transmission lines, and so onuntil the last data-cell boundary is reached. So, for the example shownin FIG. 7, the worst case timing margin bit sequence for the aggressortransmission lines is 011010. This worst case timing margin bit sequencefor the aggressor transmission lines will shift the victim transmissionline timing in one direction (i.e., shift the rising edge early). Toshift the victim transmission line timing in the opposite direction(i.e., shift the rising edge late), all the bits on the aggressortransmission lines are inverted. Thus, for the example shown in FIG. 7,the complementary worst case timing margin bit sequence for theaggressor transmission lines is 100101.

At this point it should be noted that the absolute worst case timingerror occurs in one direction (i.e., the rising edge occurs earliest)when the worst case timing margin bit sequence for the victimtransmission line 34 is transmitted on the victim transmission line 34at the same time as the worst case timing margin bit sequence for theaggressor transmission lines is transmitted on the aggressortransmission lines. Similarly, the absolute worst case timing erroroccurs in the opposite direction (i.e., the rising edge occurs latest)when the complementary worst case timing margin bit sequence for thevictim transmission line 34 is transmitted on the victim transmissionline 34 at the same time as the complementary worst case timing marginbit sequence for the aggressor transmission lines is transmitted on theaggressor transmission lines.

At this point it should be noted that, although the above-describedtechnique for determining the worst case timing margin bit sequences isdescribed above with respect to rising edge timing, this technique isdirectly applicable to falling edge timing as well.

Referring to FIG. 8, there is shown an illustration of how reflectionnoise is added on the victim transmission line 34 when the worst casetiming margin bit sequence for the victim transmission line 34 istransmitted on the victim transmission line 34. The resultant waveformshows the linear sum of the 3 SBR waveforms time shifted accordingly.

The SBR of the IC device 32 is also used to obtain the worst case bitsequences for both the victim transmission line 34 and the adjacentaggressor transmission lines (not shown) for determining the worst casevoltage margin of the IC device 32. These worst case voltage margin bitsequences are obtained by first determining the worst case voltagemargin bit sequence for the victim transmission line 34. This isaccomplished by examining the first waveform 60.

Referring to FIG. 9, the first waveform 60 is examined to determine thepolarity of the SBR of the IC device 32. That is, the worst case voltagemargin bit sequence for the victim transmission line 34 that willproduce a worst case input low voltage margin on the victim transmissionline 34 is a logic zero bit preceded by four bits whose values depend onthe polarity of the SBR of the IC device 32 at the center of eachdata-cell. Thus, the first waveform 60 is examined to determine thepolarity of the SBR of the IC device 32 at the center of each data-cell.If the polarity at the center of a data-cell is positive, then theassociated bit in the worst case voltage margin bit sequence for thevictim transmission line 34 is a logic one. Conversely, if the polarityat the center of a data-cell is negative, then the associated bit in theworst case voltage margin bit sequence for the victim transmission line34 is a logic zero.

The order of the bits in the worst case voltage margin bit sequence forthe victim transmission line 34 is determined by the order of thedata-cells. That is, the bit value determined from the polarity of themost recent data-cell is the first bit in the worst case voltage marginbit sequence for the victim transmission line 34, the bit valuedetermined from the polarity of the next most recent data-cell is thesecond bit in the worst case voltage margin bit sequence for the victimtransmission line 34, and so on until the last data-cell is reached. So,for the example shown in FIG. 9, the worst case voltage margin bitsequence for the victim transmission line 34 is 00100. As previouslymention, this worst case voltage margin bit sequence for the victimtransmission line 34 will produce a worst case input low voltage marginon the victim transmission line 34. To produce a worst case input highvoltage margin on the victim transmission line 34, the last bit ischanged to a logic one and the precursor bits are inverted. Thus, forthe example shown in FIG. 9, the complementary worst case voltage marginbit sequence for the victim transmission line 34 is 11011.

To obtain the worst case voltage margin bit sequence for the aggressortransmission lines, the second waveform 62 is examined. Referring toFIG. 10, the second waveform 62 is examined to determine the polarity ofthe SBR of the IC device 32. That is, the worst case voltage margin bitsequence for the aggressor transmission lines is five bits long. Thevalues of the five data bits depend on the polarity of the SBR of the ICdevice 32 at the center of each data-cell. Thus, the second waveform 62is examined to determine the polarity of the SBR of the IC device 32 atthe center of each data-cell. If the polarity at the center of adata-cell is positive, then the associated bit in the worst case voltagemargin bit sequence for the aggressor transmission lines is a logic one.Conversely, if the polarity at the center of a data-cell is negative,then the associated bit in the worst case voltage margin bit sequencefor the aggressor transmission lines is a logic zero.

The order of the bits in the worst case voltage margin bit sequence forthe aggressor transmission lines is determined by the order of thedata-cells. That is, the bit value determined from the polarity of themost recent data-cell is the first bit in the worst case voltage marginbit sequence for the aggressor transmission lines, the bit valuedetermined from the polarity of the next most recent data-cell is thesecond bit in the worst case voltage margin bit sequence for theaggressor transmission lines, and so on until the last data-cell isreached. So, for the example shown in FIG. 10, the worst case voltagemargin bit sequence for the aggressor transmission lines is 01001. Thisworst case voltage margin bit sequence for the aggressor transmissionlines will produce a worst case input low voltage margin on the victimtransmission line 34. To produce a worst case input high voltage marginon the victim transmission line 34, all the bits on the aggressortransmissions are inverted. Thus, for the example shown in FIG. 10, thecomplementary worst case voltage margin bit sequence for the aggressortransmission lines is 10110.

At this point it should be noted that the absolute worst case voltageerror occurs for low voltage when the worst case voltage margin bitsequence for the victim transmission line 34 is transmitted on thevictim transmission line 34 at the same time as the worst case voltagemargin bit sequence for the aggressor transmission lines is transmittedon the aggressor transmission lines. Similarly, the absolute worst casevoltage error occurs for high voltage when the complementary worst casevoltage margin bit sequence for the victim transmission line 34 istransmitted on the victim transmission line 34 at the same time as thecomplementary worst case voltage margin bit sequence for the aggressortransmission lines is transmitted on the aggressor transmission lines.

Referring to FIG. 11, there is shown an alternative embodiment of thepresent disclosure wherein a data transmission system 90 comprises adriver 92 and a receiver 94. The driver 92 includes a plurality of datatransmitters 96 for transmitting data on a corresponding plurality oftransmission lines 98. The receiver 94 includes a correspondingplurality of data receivers 100 for receiving the data transmitted onthe plurality of transmission lines 98. The corresponding datatransmitters 96, transmission lines 98, and data receivers 100 arearranged such that there is a victim (V) data transmitter 96 b,transmission line 98 b, and data receiver 100 b, surrounded by adjacentaggressor (A1 and A2) data transmitters 96 a and 96 c, transmissionlines 98 a and 98 c, and data receivers 100 a and 100 c.

The receiver 94 also includes a comparator circuit 102 comprising acomparator device 104 and a clock multiplier 106 for acquiring thetiming and voltage characteristics of the data transmitted ontransmission line 98 b. It should be noted that although only onecomparator circuit 102 is shown, a plurality of such comparator circuitscould be provided (e.g., one for each transmission line 98).

The comparator circuit 102 operates by sampling the data transmitted ontransmission line 98 b at a rate that is faster than the rate at whichthe data is transmitted on the transmission line 98 b. Thus, the clockmultiplier 106 multiplies the clock signal, CLK, to provide thecomparator device 104 with the appropriate sample rate. It should benoted that multiple phase-shifted clock signals may alternatively beused instead of the clock multiplier 106 to provide the comparatordevice 104 with the appropriate sample rate.

A comparison voltage, Vc, is provided to the comparator device 104 fordetermining the voltage level of the data transmitted on thetransmission line 98 b. The output (R) of the comparator device 104 isthus an indication of the voltage level of the data transmitted on thetransmission line 98 b. It should be noted that the level of thecomparison voltage, Vc, is typically updated based upon feedbackreceived from the output (R) of the comparator device 104.

The comparator circuit 102 is beneficially contained in the receiver 94such that the worst case performance characteristics of the entire datatransmission system 90 can be determined in accordance with the presentdisclosure as described in detail above.

Referring to FIG. 12, there is shown another alternative embodiment ofthe present disclosure wherein a data transmission system 110 comprisesthe driver 92 and a receiver 94′ having an analog-to-digital convertercircuit 112. The analog-to-digital converter circuit 112 operatessimilar to the comparator circuit 102 of FIG. 11 by acquiring the timingand voltage characteristics of the data transmitted on transmission line98 b by sampling the data transmitted on transmission line 98 b at arate that is faster than rate at which the data is transmitted on thetransmission line 98 b. Similar to the comparator circuit 102 of FIG.11, it should be noted that although only one analog-to-digitalconverter circuit 112 is shown, a plurality of such analog-to-digitalconverter circuits could be provided (e.g., one for each transmissionline 98).

The analog-to-digital converter circuit 112 comprises aanalog-to-digital converter 114 and the clock multiplier 106. The clockmultiplier 106 multiplies the clock signal, CLK, to provide theanalog-to-digital converter 114 with the appropriate sample rate. Again,it should be noted that multiple phase-shifted clock signals mayalternatively be used instead of the clock multiplier 106 to provide theanalog-to-digital converter 114 with the appropriate sample rate.

Similar to the comparator circuit 102 of FIG. 11, the analog-to-digitalconverter circuit 112 is beneficially contained in the receiver 94′ suchthat the worst case performance characteristics of the entire datatransmission system 110 can be determined in accordance with the presentdisclosure as described in detail above.

At this point it should be noted that measuring the single bit responses(SBRs) and determining the worst case bit sequences in accordance withthe present disclosure as described above typically involve theprocessing of input data and the generation of output data to someextent. This input data processing and output data generation may beimplemented in hardware or software. For example, specific electroniccomponents may be employed in a data transmission system or in a testingapparatus for implementing the functions associated with measuring thesingle bit responses (SBRs) and determining the worst case bit sequencesin accordance with the present disclosure as described above.Alternatively, a processor operating in accordance with storedinstructions may implement the functions associated with measuring thesingle bit responses (SBRs) and determining the worst case bit sequencesin accordance with the present disclosure as described above. If such isthe case, it is within the scope of the present disclosure that suchinstructions may be transmitted to a data transmission system or atesting apparatus via one or more signals.

The present disclosure apparatus and method described herein suffer fromnone of the drawbacks associated with prior art as described above sincethe absolute worst case performance is calculated based upon waveformsproduced by single pulses. Also, in accordance with the presentdisclosure, a measurement instrument can be measured in advance and aninverse transfer function can be applied to null-out ISI inherent in themeasurement instrument.

The present disclosure apparatus and method are particularly useful forhigh-speed data transmission systems which have multiple reflections andsignificant coupling between lines such as, for example, a high-speed,low-cost memory bus.

The present disclosure is not to be limited in scope by the specificembodiments described herein. Indeed, various embodiments of andmodifications to the present disclosure, in addition to those describedherein, will be apparent to those of ordinary skill in the art from theforegoing description and accompanying drawings. Thus, such otherembodiments and modifications are intended to fall within the scope ofthe present disclosure. Further, although the present disclosure hasbeen described herein in the context of a particular implementation in aparticular environment for a particular purpose, those of ordinary skillin the art will recognize that its usefulness is not limited thereto andthat the present disclosure can be beneficially implemented in anynumber of environments for any number of purposes. Accordingly, theclaims set forth below should be construed in view of the full breadthand spirit of the present disclosure as described herein.

The invention claimed is:
 1. A transmitter integrated circuit for use in a signaling system in which the transmitter integrated circuit is to be coupled to a receiver integrated circuit via transmission lines that form a digital bus, the transmitter integrated circuit comprising: data transmitters to each transmit data over respective ones of the transmission lines to the receiver integrated circuit; each of the data transmitters to transmit in parallel a test data signal to the receiver integrated circuit to determine a performance characteristic of the signaling system.
 2. The transmitter integrated circuit of claim 1, where each data transmitter comprises a pulse generator to generate a single bit pulse as the test data signal transmitted by the respective data transmitter.
 3. The transmitter integrated circuit of claim 1, where: the transmission lines are aggressor transmission lines; the signaling system is such that the transmitter integrated circuit is to be coupled to the receiver integrated circuit also via a victim transmission line of the digital bus; the data transmitters are aggressor-line data transmitters; the transmitter integrated circuit further comprises a victim-line data transmitter to transmit data over the victim transmission line to the receiver integrated circuit; and the victim-line data transmitter is to remain inactive when each of the aggressor-line data transmitters are to transmit in parallel a test data signals to the receiver integrated circuit.
 4. The transmitter integrated circuit of claim 3, where the transmitter integrated circuit is to cause the aggressor-line data transmitters to transmit the test data signals to the receiver integrated circuit in association with a signaling system operation in which the receiver integrated circuit is to measure, on a receiver coupled to the victim transmission line, a response to the transmitting of the test data signal by the aggressor-line data transmitters.
 5. The transmitter integrated circuit of claim 1, where the data transmitters are to transmit the test data signals in a manner that is synchronized across the data transmitters, and where the performance characteristic is a characteristic that affects relative transmission of data over respective ones of the transmission lines.
 6. The transmitter integrated circuit of claim 1, where the transmitter integrated circuit further comprises a processor in the signaling system and where the transmitter integrated circuit is to cause the test data signal to be transmitted by each data transmitter to determine the performance characteristic of the signaling system.
 7. The transmitter integrated circuit of claim 1, where the test data signal is common to each of the data transmitters.
 8. A transmitter integrated circuit for use in a signaling system in which the transmitter integrated circuit is to be coupled to a receiver integrated circuit via transmission lines that form a digital bus, the transmission lines including both aggressor transmission lines and a victim transmission line, the transmitter integrated circuit comprising: aggressor-line data transmitters to each transmit data over respective ones of the aggressor transmission lines to the receiver integrated circuit, and a victim-line data transmitter to transmit data over the victim transmission line to the receiver integrated circuit; each of the aggressor-line data transmitters to transmit in parallel a same test data signal to the receiver integrated circuit to determine a performance characteristic of the signaling system, at a time when the victim-line data transmitter is not to transmit the same data signal to the receiver integrated circuit.
 9. The transmitter integrated circuit of claim 8, where each aggressor-line data transmitter comprises a pulse generator to generate a single bit pulse as the same test data signal.
 10. The transmitter integrated circuit of claim 9, where the transmitter integrated circuit is to cause the aggressor-line data transmitters to transmit the same test data signal to the receiver integrated circuit in association with a signaling system operation in which the receiver integrated circuit is to measure a response to the transmitting of the test data signal by the aggressor-line data transmitters on a receiver coupled to the victim transmission line.
 11. The transmitter integrated circuit of claim 8, where the performance characteristic is an electromagnetic coupling effect between the aggressor transmission lines and the victim transmission line.
 12. A transmitter integrated circuit for use in a signaling system in which the transmitter integrated circuit is to be coupled to a receiver integrated circuit via transmission lines that form a digital bus, the receiver integrated circuit having at least one receiver to measure a response to transmission of synchronized test signals transmitted by the transmitter integrated circuit, wherein the transmitter integrated circuit comprises: data transmitters to each transmit data over respective ones of the transmission lines to the receiver integrated circuit; each of the data transmitters to transmit in parallel one of the synchronized test signals to the receiver integrated circuit, to determine a performance characteristic of the signaling system.
 13. The transmitter integrated circuit of claim 12, where the transmission lines include two aggressor transmission lines and where the transmitter integrated circuit is to be coupled to the receiver integrated circuit also via a victim transmission line of the digital bus, and where the at least one receiver to measure the response includes a victim-line receiver coupled to the victim transmission line.
 14. The transmitter integrated circuit of claim 13, where the transmitter integrated circuit further comprises a processor in the signaling system and where the processor is to cause the synchronized test signals to be transmitted by aggressor-line data transmitters to determine the performance characteristic of the signaling system.
 15. The transmitter integrated circuit of claim 12, where each data transmitter comprises a pulse generator to generate a single bit pulse as a test data signal of the synchronized test signals, and where the synchronized test data signals comprise the single bit pulses of respective ones of the data transmitters, transmitted simultaneously by each of the data transmitters.
 16. The transmitter integrated circuit of claim 15, where the performance characteristic is a characteristic that affects relative transmission of data over the transmission lines.
 17. The transmitter integrated circuit of claim 16, where the performance characteristic is an electromagnetic coupling effect between aggressor transmission lines of the transmission lines of the digital bus and a victim transmission line of the digital bus.
 18. The transmitter integrated circuit of claim 15, where the receiver integrated circuit comprises a receiver for each respective transmission line of the transmission lines, each receiver to measure a single bit response comprising time-varying artifacts from the transmission of the single bit pulse over the respective transmission line. 